Posted
by
BeauHDon Wednesday March 22, 2017 @09:25PM
from the maximized-potential dept.

An anonymous reader quotes a report from Ars Technica: The silicon-based cells that make up a solar panel have a theoretical efficiency limit of 29 percent, but so far that number has proven elusive. Practical efficiency rates in the low-20-percent range have been considered very good for commercial solar panels. But researchers with Japanese chemical manufacturer Kaneka Corporation have built a solar cell with a photo conversion rate of 26.3 percent, breaking the previous record of 25.6 percent. Although it's just a 2.7 percent increase in efficiency, improvements in commercially viable solar cell technology are increasingly hard-won. Not only that, but the researchers noted in their paper that after they submitted their article to Nature Energy, they were able to further optimize their solar cell to achieve 26.6 percent efficiency. That result has been recognized by the National Renewable Energy Lab (NREL). In the Nature Energy paper, the researchers described building a 180.4 cm2 cell using high-quality thin-film heterojunction (HJ) -- that is, layering silicon within the cell to minimize band gaps where electron states can't exist. Controlling heterojunctions is a known technique among solar cell builders -- Panasonic uses it and will likely incorporate it into cells built for Tesla at the Solar City plant in Buffalo, and Kaneka has its own proprietary heterojunction techniques. For this record-breaking solar cell, the Kaneka researchers also placed low-resistance electrodes toward the rear of the cell, which maximized the number of photons that collected inside the cell from the front. And, as is common on many solar cells, they coated the front of the cell with a layer of amorphous silicon and an anti-reflective layer to protect the cell's components and collect photons more efficiently.

Eh? Well, the way I was taught to calculate a percentage increase was:

(a) 26.3 - 25.6 = 0.7
(b) 0.7/25.6 = 0.02734

It's not a percentage increase in the first place. When the power of the incident light was 100W the old solar cells would produce 25.6W of electrical power. In the same conditions the new cells provide 26.3W. So that's an increase in the delivered power of (26.3 - 25.6) / 25.6 = 2.7%. See none of the numbers being compared are percentages.

And, although the wording clearly implies an absolute relationship, the correct relative formula would be 26.3/25.6=1.03 when significant digits are accommodated (which would be a 3% relative increase).

You're making the assumption that 26.3 and 25.6 are given with the full number of significant digits (which may not be the case), or that significant digits actually matter in a percentage figure (not an actual measurement) in popular scientific journalism. Get over yourself.

26.29 rounds to 26, not 27. And, although the wording clearly implies an absolute relationship, the correct relative formula would be 26.3/25.6=1.03 when significant digits are accommodated (which would be a 3% relative increase).

26.3 (the previous record), multiplied by 1.027 (or 102.7%, or increasing by 2.7%) equals 26.29, which rounds to 26.3 (the new record).That's not elementary maths, I grant you, but I'm sure you would have spotted it if you weren't so eager for the FP.

There's a new better photovoltaic cell, that is actually produced by an actual manufacturer (Kaneka) and could soon be matched by other actual manufacturer making real cells in the real world (Panasonic and Tesla mentioned), and not simply one of those "small research team in some university lab make a small breakthrough that could increase cell effenciency. In theory. Probably within 25 years when the discovery finally reach actual production at a real-world manufacturer".

Significant digits (figures)? Fuck that shit - everyone does it incorrectly, and it's fucking retarded when done "correctly". Seriously, why the FUCK would you consider a reading of "20" to be less valid than a reading of "21" when all else (measurement device, environment, methodology, etc.) is the same? Yet "2.0x10^1" is more significant than 20? It's absurd.

Further, 26.3 / 25.6 is a calculation, not a measurement, and you can't apply significant figures to raw calculations like that without fucking e

This is only single cell solar cells, multi-junction cells have breached 46%. https://www.ise.fraunhofer.de/... [fraunhofer.de]
At this point increases in efficiency are mostly masturbation, relying on complex materials/techniques that aren't worth the cost. The big transformation will occur when they get thin film solar cells that are more efficient so you can have solar cells without making ridiculous amounts of toxic waste.

It's a standard, procedurally-generated right-wing parroting point that executes in any discussion about $NEW_GREEN_TECH:

"$NEW_GREEN_TECH generates an incredible amount of toxic waste to produce, even more than $OLD_FOSSIL_TECH!"

Veracity is not a factor in the algorithm, the statement is simply generated and echoed. It's interesting how right-wingers suddenly become concerned (if fact-deprived) environmentalists AND income-egalitarians ("The CEO of $NEW_GREEN_TECH company is going to get rich off the backs

Meanwhile, coal power plants spew radioactive waste from smokestacks, the ground is pumped full of earthquake-enabling mystery sauce for hydrofracking, and oil refineries guzzle energy to transform fossil fuels from one form to another before they're even used, all while literally causing floods of toxic waste, and nobody on the right bats an eye at those environmental disasters that happen in the process of releasing fossil CO2. They

Perhaps, but the ultimate ancestor in this thread was referring to "multi-junction cells have breached 46%", which tend to made of [wikipedia.org] things like Indium Gallium Phosphide, Gallium Arsenide, Germanium, and Indium Gallium Arsenide.

I believe the point was that that we know how to make them far more efficient than 26%, if we really want to. It just tends to require making them of relatively exotic things that probably aren't worth the trouble.

Based on a meta-analysis [nrel.gov], current PV systems have energy payback times of about 3-4 years. But that's unlikely to be accurate. Subsidized payback periods for PV systems are about 7 years, and unsubsidized payback periods are about 15 years, and both PV and non-PV costs are dominated by energy inputs.

This is laboratory stage, the hunt for better efficiency is still very useful. Other teams / companies work on industrialization of the newly found processes from a laboratory to create these things for a reasonable price. This is how science has worked for over 100 years now

Exactly. It's interesting research, but it hits diminishing returns very quickly. Cheap solar panels have gone from 8% to 16% efficiency in a few years. That's a huge win, because you get double the power output for the same investment. Getting up to 32% for the same cost will be a similar win, but that's a long way away.

The easiest way to get up around 32% efficiency is to stop using semiconductors and use concentrated sunlight to drive a turbine instead. Glass mirrors are fairly cheap per square meter.

Solar concentrators don't work for residential solar, because of the need to track the Sun. But utility-scale solar panel farms beat residential by 2.5x on cost anyway. The panels cost the same in both cases, but all the other costs are much lower for a solar farm when you install them at ground level by the hundred thousa

This is the record efficiency obtained for a SILICON solar cell, and while the title may be slightly misleading by not clarifying the summary and articles are discussing Silicon cells. This is absolutely a record, and it is of great interest and importance since such a cell would be expected to give a lower cost per watt than multijunction cells.

Seattle gets about 3.7 hours per day average insolation. It doesn't make sense to put them there until you run out of space in AZ and California. Your roi is 2x higher in those places. Worse than that, it doesn't provide energy in the winter when it's needed most. I have a house there and my summer electric bill is next to nothing.

and I have all of my roof covered that gets direct sunlight, and they still aren't powerful enough to produce enough power even in the summer to overcome the self-discharge of my SLA batteries. Here in Seattle in the winter, I might as well not even have the panels. 26% efficient would be strong enough to keep me from having to plug a charger into the wall to charge my batteries for maybe six months a year. Hopefully this will reach consumers soon.

The state of WA is almost entirely powered by hydro-electric. We already have reasonably cheap, green power right off the grid here. And you weren't satisfied with buying solar panels just once, but are interested in purchasing a second set because the first ones were so worthless.

I've found that the charger you are using makes a difference. If it is a PWM charger that cuts the voltage down to whatever the batteries take, you can lose 25-50% of the incoming wattage. For example (and note, these figures vary widely in real life since batteries require different voltages in different charging stages), a 24 volt panel feeding a PWM charger that is using a 12 volt battery, the PWM charger will not use 12 volts of the 24 coming in. However, a MPPT controller will reduce the voltage and

And while the cost per watt of the panels goes down (and from that the cost of shipping & installation), the cost of the inverter & other electrical wiring stays relatively fixed. It's way behind the panels & batteries but it is in the thousands of dollars per installation.

if you are going to replace your roof, then have a look at this. https://techcrunch.com/2016/10... [techcrunch.com]
be cheaper than a new roof plus solar, its allegedly almost the same as just a new roof (depending on what you use)

So far the consensus of what I've read says for the long haul industrial lead acid are the best for the money. I looked at some, they had some running about 400 pounds each. Thousands of dollars but long lasting and durable. Properly cared for easily good for a decade.

Panels of the same form factor with higher-efficiency cells install in exactly the same way. 255W panels install the same way as 180W panels and 355W panels (all of the same size). They rack up onto the same hardware.

Oddly enough, the cost of micro-inverters for panels above 255W increases; and modern power-optimizing inverters actually cost the same, but fail less-often and provide more-efficient power regulation. The installation for string inverters, micro-inverters, and power-optimizing inverters i

Shipping the cells requires more energy because they're larger and heavier. It requires more shipping hardware and energy infrastructure maintenance. It requires more handling to install them, wire them, and keep them free of the energy-robbing layer of dust. Manufacturing costs increase for an array with the same output, so decay from oxidization, delamination, imbalanced arrays and overvoltage, or plain old damage costs more--as does the shipping and handling, again.

It is impossible for a 2 square meter to output 6kW anywhere in the world. Even if you had a perfect solar cell that converts all forms of solar radiation to electicity at 100% efficiency you are limited to 1.361kW per square meter. You just can't make more sunlight.

That wasn't the point. The cost differences in shipping and installation are because the panels are of various sizes and weights; if I could get an impossible device that's a cubic centimeter, 3 grams, and generates 500GW of power, I could ship it via 32 cents of postage and install it in a few minutes of labor. Do you know how much it costs just to ship the concrete to build the nuclear containment building for a reactor?

Earlier today, I set up a folding panel with sunpower cells; it was literally vertical, in a window, facing South. Total surface area.. maybe 3sqft, weighing 1lb. It was making ~20W for 4 hours, and managed to completely recharge my 130Wh battery pack in 8. Through a window. In the winter, in Canada.

The thing cost $120.

It's easy to get lost in the constant claims of breakthroughs while forgetting what an amazing time we live in. 20 years ago, this panel would have blocked out the sun and cost a months' salary.

The solar roof installed on my workplace (a large school) costs tens of thousands and won't pay for itself in 20 years.

It isn't even warrantied for that long.

It very much depends on where you are, not whether your panel is vertical or not (sure, it's BETTER to be vertical, but if you don't have enough sun in the first place, it makes virtually no difference).

We even have one of those "this is how much energy you're generating, CO2 you've saved" screens inside the building it's on. It's curren

How on *earth* did your school manage to install a large panel costing tens of thousands that can generate as little as 45W??? Can you provide more details? Cos this sounds pretty dubious. What time of day? How old is the installation? What was its rated generative capacity? Where is the school?

I mean, a typical home installation generates 3kW, and costs well under 10k.

> install a large panel costing tens of thousands that can generate as little as 45W???

He forgot to mention that it's night, and the only light is coming from the full moon and a street lamp in the parking lot.

The real problem is: 'one of those "this is how much energy you're generating, CO2 you've saved" screens'. Some people just get hopelessly irritated by stuff like that. These panels could be great, making free power, steak dinners, good jobs, curing erectile dysfunction and shitting out Tiffany cuf

The ironic thing is that both the preppers I know and the hippies both actually like photo-voltaic technology. One camp likes it because it is off grid and frees them from being dependent on a central electricity system. Another camp likes it because it is not throwing pollution into the air. Plus, it is pretty foolproof. You can get electrocuted or have a panel fall on your head... but for the most part, setup is idiot resistant, especially compared to almost any other power generation out there. Plus

Apart from the massive amounts of nasty environmental waste being produced in China (where most come from) that's threatening the potable water of a few tens of millions of people downstream.

Hydroflouric acid in particular is something you don't want in your waterways.

In northern latitudes, you'd be better off thinking about solar heat panels and suchlike to offset your energy costs, but solar PV is generally a waste of space unless you're off-grid and away-from-grid

The reason I suggest solar heat panels is because they're cheap to manufacture and maintain, making the 5-10% potential heating costs saving worthwhile aiming for.

If you wanted to get really whizzy you could store solar heat in the ground in summer and extract in winter but that's a massive complexity boost with long payoff period. On the other hand schools tend to have large open fields where the pipework for such systems can be laid relatively easily and deeply.

This is the FOURTH school I've worked at that has the same problem. The others I've worked at have deliberately refused solar installs after doing the sums.

In certain places, solar is just POINTLESS.

I'm in the UK, a major developed country the same latitude as other huge centres of population the world over. (Please don't say "Ah, yes, in the UK you won't get...." - this is exactly my point, solar is not a panacea).

And it's currently reading... ZIP. Literally I have to interpret the decimal points,

A correctly installed 10kW solar array at that latitude should peak at around 7kW. If you're seeing less than one, then someone fucked up the wiring, or most of the panels are defective. Fire whoever's responsible, and sue the company until they fix it.

FFS, mate. I live in the UK too. Your figures seem ridiculous -- your school has been had. Here in Norf London, there are hundreds of houses with solar fitted that's charging Teslas. Couldn't do that if the conversions were as poor as you assert for your school. And there is no way that at 1pm on a cloudy day a 10kW system in the UK should be generating zero. That is mad.

Don't let that experience sour you on PV solar. What you're seeing has nothing to do with the technology itself; solar works extremely well, even at high latitudes, when installed correctly. Ask any sailor, NASA engineer, or grid energy systems expert.

If you're seeing 45W during the day on a $10k+ array, sue the installer because it's malfunctioning.

BTW - You don't want vertical panels except at the poles (or temporarily when mounted on a heliostat).

Cost is not everything, that is pretty dumb economic thinking. Cost efficiency is everything, the return on capital investment. With branded solar energy systems, retained capital investment is as important as energy generated. Want it the price of a home with a top quality solar energy system versus a home without one. What premium can you start to charge on a home where the supply charge for electricity is higher than the cost of actual supply of electricity, a house that is basically black out proof. Where energy running cost for a car heads to zero.

So in mid level housing density, how close to an effective solar energy system for a two story town house, where a premium is paid, due to limited are for panels. It makes no sense with solar panels to have them anywhere else but as close as practicable to the point of demand, screw the insensate greed of the energy companies. Doing away with the electrical grid all together in suburban low density housing would be a major victory for the majority, screw the energy companies, they can pretty much choke on their own gas (tee hee).

Cost is not everything, that is pretty dumb economic thinking. Cost efficiency is everything, the return on capital investment.

With solar panels, it turns out that these two correlate quite nicely. With the exception of potential panel area limitation, cheaper panels are also more cost efficient. Although the US is also an outlier with fixed non-hardware costs (permits, labor etc.), so your experience may be somewhat different than in other parts of the world, where the cost efficiency of ordinary panels is much more obvious.

Why is this rated -1? Cost is a damn strong motivator to general adoption, and the absolute first thing that comes to mind as a barricade to entry in the current energy market.

Cost might not be the only thing that matters, but any energy source today must fulfill one of two criteria -

1. Cheap. For personal use (such as solar panels on the roof of a house) the barrier to entry is price. Your standard homeowner only has $X saved up, so even a super-efficient solar panel for $250,000 will remain out of reach.

Panels that are cheap for areas such as building roofs where grabbing every last watt isn't such a big deal, due to the availability of space. It is just getting the solar cells on the area that is the main thing.

Panels where surface area is hard to obtain (satellites is one example.) where every watt is precious. A more realistic example are solar panels on class "B" motorhomes (campervans.) There isn't much in the way of square footage, so the trick is to maximize what can be gotten.

The key word is 'buffering' , the ability to absorb excess energy. Solar and wind energy are very variable. You can store a bit of excess energy locally in your own home, but a smart grid allows you to pass it on to others who need it. Excess energy production on a larger scale becomes problematic. If you can adjust fossil energy production quickly to match so you can compensate this way, but the possibilities for storing renewable energy are minimal. They're also rather lowtech so they won't get much atten

AKA "The very large French nuclear reactor fleet in the country next door (which happens to be France)", which has some load-following ability.

"Renewables" in northern europe have the potential to replace all current carbon emitting sources - if the entire european countryside is carpetted in turbines and glazed with solar panels, at a cost several tens of times higher than the carbon-emitting sources (and the fuel) they replace.